Revision of F468 - 12 Standard Specification for Nonferrous Bolts, Hex Cap Screws, Socket Head Cap Screws, and Studs for General Use

WK46618

1. Rationale

ASTM F468 Subject: The addition of C-86 Nickel alloy on the identical property line as 686 Nickel alloy. Background: Nickel alloys C-86 and 686 have the same basic chemistry but differ in the manufacturing practices with the concern for the development of mu phase during processing of the material. Currently for Navy applications, each lot of 686 alloy is carefully reviewed before going into fastener production. The material alloy numbers provided in ASTM F467/468 as presented do not differentiate between the manufacturing processes. Little is known on the long term stability of this material over decades of in-service use for a manufactured part. Discussion: Designs used in US Naval service may be installed with little or no inspection over long periods of time, especially if service/inspection requires dry-docking. One of the primary environments for a nickel based alloy fastener is in seawater service. Table 2 of ASTM F467 and Table 2 of ASTM F468 utilize the identical material property marking without regard to the manufacturing process. This material has a tendency to migrate to the mu phase form during fabrication. Currently, there is no long term data available to show that one manufacturing process or the other results in a more stable material condition in various end-use environments over a long term (decades). Based on this, it is preferable to ensure that any fasteners produced include the alloy (C-86 or 686) and grade so as to be able to segregate the materials in their end-use location until such time that long term data becomes available. Utilizing the mechanical property marking method will not segregate the products. Having the alloy (C-86 or 686) distinctively marked with help with identification of failures and potential to identify the alloy should this become a determining factor for long term use in various environments in the future. It is therefore requested that the alloy process be identified in the part supplied by specifying the alloy (C-86 or 686) along with the material grade in the ordering and packaging information for this material. ASTM F468, sections 3.1.4 and 16.3.2